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Cephalexin (Keflex) Medical Facts
Cephalexin (Keflex) in Brief
- Active ingredient: cephalexin
- Common brand names: Keflex, Keftabs, Biocef
- Drug class: first-generation cephalosporin antibiotic
- FDA Approved:
- Chemical Formula: C16H17N3O4S
- Legal status: Prescription only
- Pregnancy Category: B
- Habit forming? No
FDA approved uses
- Respiratory tract infections caused by Streptococcus pneumoniae
and Streptococcus pyogenes
- Otitis media due to Streptococcus pneumoniae, Haemophilus influenzae,
Staphylococcusaureus, Streptococcus pyogenes, and Moraxella catarrhalis
- Skin and skin structure infections caused by Staphylococcusaureus
and/or Streptococcus pyogenes
- Bone infections caused by Staphylococcusaureus and/or Proteus mirabilis
- Genitourinary tract infections, including acute prostatitis, caused
by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae
Cephalexin "pros" and "cons"
- Advantages:
- excellent safety record
- very low incidence of allergic reactions
- may be taken without regard to food
- superior to penicillin in the streptococcal throat infection 3
- Disadvantages:
- short half-life requires QID dosing
- less active than cefatrizine and cefaclor against Escherichia
coli, Klebsiella pneumoniae and Proteus mirabilis 2
Time for Cephalexin to clear out the system
Cephalexin mean half-life is 50 to 80 min. It may take 4 to 5 hours
to clear out of the system.
Further reading
References
- 1. Disney FA, Dillon H, Blumer JL, Dudding BA, McLinn SE, Nelson
DB, Selbst SM. Cephalexin and penicillin in the treatment of group
A beta-hemolytic streptococcal throat infections. Am J Dis Child.
1992 Nov;146(11):1324-7. PubMed
- 2. Luh KT, Chao HP, Ho SW, Hsieh WC. Comparison of in vitro antibacterial
activity of four oral cephems: cephalexin, cefaclor, cefatrizine and
cefadroxil. Zhonghua Min Guo Wei Sheng Wu Ji Mian Yi Xue Za Zhi. 1984
Feb;17(1):11-8. PubMed
- 3. Disney FA, Dillon H, Blumer JL, Dudding BA, McLinn SE, Nelson
DB, Selbst SM. Cephalexin and penicillin in the treatment of group
A beta-hemolytic streptococcal throat infections. Am J Dis Child.
1992 Nov;146(11):1324-7. PubMed
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